Multi-variable state closed-loop control for a steam generator of a thermal power plant

1. A method for closed-loop control of a plurality of state variables in a steam generator of a thermal power plant, comprising:

providing a spatially discretized steam generator model of the steam generator of the thermal power plant, wherein the steam generator has at least one evaporator and a superheater, wherein the steam generator has a plurality of discretized volume elements with a constant volume, and wherein the spatially discretized steam generator model has at least one of energy and mass balance set by way of the plurality of discretized volume elements;

simultaneously controlling the plurality of state variables using a multi-variable state controller, the multi-variable state controller being a linear quadratic controller, wherein the multi-variable state controller uses the spatially discretized steam generator model.

2. The method as claimed in claim 1 , wherein the plurality of state variables simultaneously controlled by the multi-variable state controller are a temperature, a pressure and/or an enthalpy of a steam generator medium of the steam generator, at least a fresh steam pressure, an evaporator output enthalpy and superheater output temperatures of the steam generator.

3. The method as claimed in claim 1 , wherein manipulated variables of the multi-variable state controller are selected from the group consisting of: mass flows of the steam generator, a fuel mass flow, a feedwater mass flow, and an injection mass flow in a superheater or injection mass flows in superheaters.

4. The method as claimed in claim 1 , wherein manipulated variables of the multi-variable state controller are subject to statistical feedforward control.

5. The method as claimed in claim 1 , wherein an overall observer is used during multi-variable state control, with the use of which state variables and/or disturbance variables are estimated at the steam generator.

6. The method as claimed in claim 5 , wherein at least one of a Kalman filter and an extended Kalman filter is used in the overall observer.

7. The method as claimed in claim 6 , wherein at least one of the Kalman filter and the extended Kalman filter is designed for linear quadratic state feedback.

8. The method as claimed in claim 1 , wherein the spatially discretized steam generator model is used in an overall observer.

9. The method as claimed in claim 1 , wherein reference values are predetermined centrally during the multi-variable state control, which reference values are used for feedforward control and for state control during the multi-variable state control.

10. A device for closed-loop control of a plurality of state variables in a steam generator of a thermal power plant, wherein the multi-variable state controller as claimed in claim 1 controls the plurality of state variables.